In general, in an imaging element such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor (CIS), color mixing (color crosstalk) affected by adjacent pixels occurs.
In a rough classification, the color mixing is divided into electrical color mixing attributed to the entry of a diffused charge inside the substrate and optical color mixing in which incident light leaks into an adjacent pixel due to diffused reflection or the like.
These color mixings are a factor in adversely affecting the image quality, such as deteriorating the color reproducibility.
So, there have been proposed a technique of providing each color with a coefficient for color mixing correction to enable in-plane uniform correction, a technique of similarly carrying out in-plane uniform correction by the F-number, and so forth (refer to e.g. patent document 1).
Furthermore, in general, simultaneously with the color mixing, the amount of light that does not contribute to photoelectric conversion of a photodiode exists in the pixel due to light absorption and so forth, and vignetting occurs on a pixel-by-pixel basis.
Such vignetting is referred to as pixel shading and is influenced by interface reflection, light absorption into poly-silicon or the like forming a transistor, and so forth. The pixel shading has in-plane distribution similarly to the color mixing and is a factor in deteriorating the image quality.
So, there have been proposed correcting devices in which the distribution in the imaging plane is considered only about this pixel shading (refer to patent documents 2 and 3). They are systems to carry out shading correction of a signal from the sensor output obtained with the color mixing ignored.